Desert Valley Biker

Above is a picture I drew of a tough biker guy. I scanned it into the computer along with rock formations and flowers that I drew as well. I took an illustrator class already so I know the basics, but still trying to figure out how to illustrate this. I want to make it look like a basic illustration with color. I want the lines to be black and bold and the background to be a pinkish bluish sunset. I want the rock formations to look very detailed and realistic.